The core of any Lunetta system are the oscillators. Lunettas use only square wave oscillators, usually made by very simple logic. Typically, Lunetta oscillators have a relatively limited frequency range - just a couple of octaves - because the circuits are so simple. That is much less of a problem than it seems, because most of the frequency setting is done down stream though various other circuits. Thus, while a good Lunetta oscillator does in fact have a frequency knob, the are used more like clocks than a conventional VCO in an analog modular system.

Bugbrand already posted a nice appropriate Lunetta style oscillator which I'm reposting here to get things started off. (Click on the pic to see it full-sized).

This is a good one to start with, The main OSC uses a single inverter with an RC (Resistor Capacitor) network to set the frequency of the OSC. The sync out is a nice bonus with this circuit, but the sync feature is not necessary.

There are other variations of the inverter OSC which I hope people will post here. Also, this topic is a place to post questions and comments about oscillators built with simple logic.

Note, it is possible to use an analog VCO with a Lunetta, but this can present problems with interface circuits. For example, Digital logic likes input swings between 0 V and Vcc.

So, let's see some more oscillators here and questions and discussion._________________--Howard
my music and other stuff

For example, you make simple oscillators using digital inverters with RC networks. If you uses NAND gates instead of inverters, you get some sort of neat modulation when you hook up another oscillator to one of the free gate inputs.

For example, you make simple oscillators using digital inverters with RC networks. If you uses NAND gates instead of inverters, you get some sort of neat modulation when you hook up another oscillator to one of the free gate inputs.

Couldn't one use a NOR gate instead and let the extra input act as a mute? That means you could use it as a some kind of VCA, right? turning on and off the OSC?

There you go. That's what Lunetta originally came up with. Just use NAND gates. A two input inverting gate makes a great modulator. You can built it into the oscillator, or just patch the oscillator into a two input gate. The other input is the "gate" or "mute" signal. Use two oscillators of different frequencies in you get a neat 50 cent modulator.

Here is a G2 patch that shows how a gate can be used as a modulator. I'll probably start a new topic about this because it is so basic. This patch works with the free G2 demo. I strongly recommend everyone interested in Lunettas try out the G2 demo. It has some basic logic circuits you can use to try things out before breadboarding. I'm not pushing that people buy a G2, but this is a great test bed.

i know you said square but here is a 4049 tri / sine ( well close enough ) lfo i've used. its not perfect but very usable. using a smaller C1 will get it up into audio range, not sure how well the shape will stay put up there though

The 4060 looks like a fun chip but just remember that it is a ripple counter. This means that the outputs don't all change at the same time, but rather 'cascade' one after the other. Now the time it takes to do this is only milliseconds, but it's enough to bugger up circuits like D/A converters. This may not matter in a Lunetta ("it's a feature, not a bug"), but if the timing of the circuit is critical then you'll want to use a synchronous counter instead.

you can sneak some triangleish waves from circuits similar to the first one in this thread

you take your audio signal out from the input of the inverter
usually works best if you use a resistor for this
this also works with other logic chips if square waves ever upset you
and of course these triangles dont always like running into other logic afterwards

wiring a cap between the signal and ground to make a passive low pass filter is also a simple way to "smooth out" the signal

and for oscillators derived from nand gates
i have a fondness for wiring the 4 nands in a ring ( so 1 gates 2 gates 3 gates 4 gates 1 ....) the way it slides and jumps frequencies is really something i have yet to hear from other synths oh and you need to wire voltage to one of them to "jump start" it or you can wire inputs to have the nand ring be influenced by other circuits

Wow, sometimes things take a lot longer than expected... With the first mentions of Lunettas I really thought I'd get a few ideas built up quite quickly, but a month down the line and I've only just completed my first module. Cripes.. (well, actually, I built two of these modules at the same time)

This is a 40106 quad-oscillator bank (along the lines of the schematic at the top of this page) and a 4077 XNOR.

Each Osc has three ranges (low freq to audio) and Oscs 2 & 4 can be sync'd to either Osc1 or Osc3 - the Sync sound is damn cool, but I haven't really tested it yet in lower freq modes...

The Leds are all just low current 3mm hung straight off the outputs via 4k7 resistors..

Yeah, thanks, I love bananas! (apart from normalisation - that's the one annoyance with 'em) - these all come from Rapid in the UK - the quality of these ones is really good and they're very well priced (also for their stackable plugs) - I don't think the Futurlec ones measure up in terms of quality (though I've not tried them - they look very much like the ones stocked in maplins which I tried once and found to be crap, both in quality and feel). Rapid are a fantastic company and do now do exports - I'm not sure how affordable it is to the US though, especially with the weak dollar... (but I just noticed you can make your shopping cart there in $). Knobs are also from there (again, very good price - I think I sent you the link to 'em a while back?!) - they've got a nice slightly rubbery feel to 'em.

Yeah, I'll certainly post future module details - I've got plenty of ideas brewing - but seems like I'm not now spending 24/7 building stuff as I was much of the past couple of years (y'know, sanity is important!)....

Edit - oh yeah, I'm now generally using water-slide-decals on plain 3mm alu for panels (where previously I'd been engraving anodized panels) because I felt I needed to improve the labeling situation. These are working well for me now. I could post the FrontDesigner file if anyone is interested?_________________http://www.bugbrand.co.ukhttp://www.bugbrand.blogspot.com

yes id love the template AND info on where and what is up with the decals...how they work , where to buy em and etc...i just got a dymo to help with some labelling as my modules dont look so good (see the IKEA THREAD for a new photo of my modulars second rack)

i do know that the schematic at the top of the page and the one he used for the above modual are diferent. the above modual uses 2 spst's for the synch. he has the schem on his website for that one. i also get thrown by those weird schematic blocks. i think they are semi open ended, like it could be a switch or jack etc... i could be wrong though?

ok so i have been working on a 40106 osc for alittle while now. it is basically a mix of bugs schematic with the sych and synthmongers with the ramp and trigger out. i breadboarded it and it seems that the ramp is super faint now i can barley hear it? i could put up the hand drawn schematic if anyones interested? the only changes are(synthmonger schem) the 1m on the cv in to a 100k the 1m on the atten. pot to a 100k..

bbob, sweet image, I love those protoboards, I prototype anything low frequency and low power on them. Seeing this thread has inspired me to add Lunettas to the EChucK project - what a great way to reuse classic circuit designs! I need to go read up on prior Lunetta posts, Lunettas are cool!_________________"Let's make noise for peace." - Kijjaz

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